The purpose of the proposed study is to determine net acid balance in infants and children with uremic acidosis or with the proximal or distal form of renal tubular acidosis (RTA). The hypothesis to be tested is that children with uremic acidosis or distal RTA are in positive net acid balance as opposed to children with proximal renal tubular acidosis who are in zero net acid balance. This difference may explain the absence of bone disease in proximal RTA and the presence of nephrocalcinosis and hypercalciuria in distal RTA and bone disease in uremic acidosis through the recruitment of bone salts as buffers with resultant dissolution of bone and release of calcium. Net acid balance studies will be performed on children with various forms of renal acidosis. This involves meticulous collection and analysis of diet, stools, and urine to determine all components of intake and output of acid. The results should aid the understanding of the pathophysiology of various forms of renal acidosis and lead to more effective therapy.